Most of modern methods of product recommendation or digital advertising are to find out one or more products or information, interesting to a user, from the user's past browsing history and then post the one or more products or information in the web page presently browsed by the user, in order to enhance the opportunity for the user to purchase the promoted product or click the posted advertisement. However, such an analysis process mainly focuses on discovering a specific item or goods appearing on the website browsed by a user, but seldom focuses on discovering inter-site browsing attributes of the user.